Recovery of formic esters used as solvents of cellulose compounds.



FED STATES rA E 1 race.

JAcQUEs DUCLAUX, or rears, Ensues.

RECOVERY OF FORMIG ESTERS USED AS'SOLVENTS CELLULOSE COMPOUNDS.

iamzsrn No Drawing.

To all 1127mm it may concern:

Be itknown that I, JACQUES DUCLAUX, a citizen of France, residing in Paris, France, have invented certain new and useful IDIIHOVQIIICI'ltS in the Recovery of For-i is, however, possible to employ two of these esters, namely, ethyl and methyl fol-mates under very satisfactory conditions as re gards economy by the adoption of the following process which constitutes the subject-matter of the present invention, and has for its object the recovery of the-vapors of theseformates and their regeneration so as to permit the solvents to be used over again. It has been found by experiment that the cost of recovering these ester compounds can be considerably reduced, and a study of the conditions of their formation shows in fact that it is possible to produce them with the full theoretical yield by the direct action of formic acid uponmethyl and ethyl alcohol even when largely diluted with water. The only precaution to be taken consists in adding an excess of alcohol in such a manner that the acid is at the commencement of the process in contact with a greater quantity of alcohol than it is able to convert, and it is also necessary to provide rectifying apparatus adapted to separate completely the ester which is formed, from the excess of alcohol, which can be easily effected since their boiling points differ to the extent of approximtely 30 C. Under the above-mentioned conditions the conversion of the formic acid takes place rapidly and is complete, while if an excess of alcohol is not present the conversion is not only incomplete but takes place extremely slowly. The amount of alcohol required varies according to the efiiciency'of the rectifying apparatus, but in general it is only necessary to employ double the quantity theoretically re- Sp'ecification of Letters Patent.

" Patented Feb.9, 1915.

Application filed January 31. 1913. Serial N01 745,382.

.quired for the conversion of the formic acid Instead of using formic acid itself thereaction with the alcohol can be obtained by a solution of a, formate added to, an equivalent quantity of an acideven when this acid vwill not completely replace the formic acid in the formate.

This process for the production of methyl and ethyl formates as applied to the manufacture of artificial silk or other cellulose products having an ester base constitutes a special feature of the invention. The process can be utilized forthe treatment of solutions containing either formic acid or formates obtained by the, recovery of the vapors of these ester compounds given off to the surrounding air during the manufacture of cellulose products having an" ester base according to the invention, and in the case of formate vapor this method of treatment is essential owing to the fact that thev re-- covery of the ester gives only dilute solulates to the recovery of the vapors of ethyl tions of formates which cannot be employed and methyl formates is rendered possible by the property these vapors possess of being immediately saponified byaqueous solutions of alkalis. Experiments have shown that if air containing the vapors of these esters is permitted to bubble through water containing in solution or suspension a basic substance, even though a very weak one, or a salt giving an alkaline reaction, the air is completely freed from these vapors even when it only contains a very small proportion of the ester compounds, such for instance as a few grams per cubic meter. The solution of the vapors of the methyl and ethyl formates in the water is extremely rapid although these formates are themselves only slightly soluble, and this rapidity of solution of the vapors accounts for their rapid decomposition by the alkali. which is a necessary condition in view of the very small proportion of the vapors of the ester compounds which the air contains and which it is necessary, however, to recover owing to their costliness. By the pasis set free in the form in which it proviously existed in th vapors can may be to decompose the forniicester, and in this so 'that the loss of the solvents is extremely case the liquid. issuing from the apparatus contains both the alcohol and the formate and can be employed for the regeneration of the formic ester without previous rectiiication.

The formate solution obtained as above described, whatever the base combined with the formic acid, is treated by a'quantity of strong acid (for example hydrochloric, nitric, sulfuric acid or mixtures of these) which is just sufficient to set free the formic acid. There is then added, if necessary, methyl or ethyl alcohol until an excess of alcohol is resent, as already explained above, and y distillation in a rectifying apparatus as already explained a formic ester is first obtained and afterward alcohol which are used over again in the process. All these reactions can be effected with a vield almost equal, to the theoretical yield small.

The'economy of the prqcess can also be increased by employing as solvents of nitrocellulose or other cellulose esters instead of pure methyl or ethyl formates, mixtures of esters employed as solvents of cellulose com-" pounds in the manufacture of cellulose articles, comprising absorbing the vapors of the solvent in water containing an alkaline agent and adding a strong acid and a large excess of methyl or ethyl alcohol to the dilute solution, and distilling off the formic ester formed.

2. In a process for the recovery of formic est'ers employed as solvents of cellulose compounds in the manufacture of cellulosi'c articles, absorbing in water containing an alkaline agent the vapors of the esters'from air laden with the vapors.

3. In a process for the recovery of formic esters employed as solvents of cellulose compounds in the manufacture of cellulosic articles, absorbing in water containing an alkaline agent the vapors of the esters from air laden with the vapors and recovering the alcohol and aiKaline for-mates formed.

In witness whereof, I have hereunto signed my name in the presence of two subscribing witnesses. 1

\ JACQUES DUCLAUX.

Witnesses:

LUGIAN MEMMINGER, RENE BARDY. 

